1. Field of the Invention
This invention relates to drinking cups, in particular portable electric cups adapted to fit in standard vehicle cup holders and to electrically be connected to vehicle cigarette lighter sockets.
2. Background of the Prior Art
It is not unusual for people to drive their vehicles for one hour or more to commute to work, and some workers, such as truckers, drive many hours each day. Consequently, most vehicles contain receptacles which hold drinking cups and cans.
Coffee is a favorite beverage of people driving long distances. Most individuals drink from disposable coffee cups when traveling in a vehicle, which are typically made from styrofoam or cardboard. The disadvantage of disposable cups is that they are flimsy, often spilling their liquid. In addition, disposable cups do not provide adequate insulation between the hot liquid contained therein and a person's hand.
Non-disposable vehicle drinking cups have become popular. The non-disposable cups are more attractive than disposable cups, are much sturdier, and usually provide better insulation. Non-disposable vehicle cups are typically made from metal, plastic, or ceramics. The disadvantage of metal and ceramic cups is that they retain heat from the coffee. If a beverage, such as coffee, is very hot, the metal or ceramic cups can end up burning a person's hand and/or lips. Plastic, on the other hand, is not as strong as metal or attractive as ceramic, but is a better insulator.
Insulated cups are designed so that the exterior of the cup remains substantially at ambient temperature, while the temperature of the liquid contained therein remains above or below the ambient temperature for longer periods of time than liquid contained within cups that are not insulated. Insulated cups typically consist of inner and outer walls with an insulating space therebetween, and are formed of a single material, such as metal, plastic, or ceramics. Plastic insulated cups are popular because the drinking lip tends to be significantly cooler than the hot liquid contained in the cup, and is thus safe to drink from, especially while driving. Double walled metal cups, although sturdier and often more esthetically desirable (for example, stainless steel), absorb and retain more heat from the liquid contained in the cup than a similarly constructed plastic cup, and therefore, can potentially cause burns or at least make drinking from such a cup uncomfortable. The present invention recognizes the need to incorporate the advantages of plastic and metal into one cup.
The present invention also recognizes that hot beverages, such as coffee, contained in traditional non-disposable vehicle cups cool relatively quickly, even when contained in insulated vehicle cups. Therefore, there is a need to safely keep drinks hot during extended vehicular travel. Clearly, it is well known to combine a heating element and a liquid container to heat the liquid contained therein. Electric kettles are a good example. However, these liquid containers use metal inside walls to quickly transfer the heat from the heating elements to the liquid contained therein, and often incorporate an insulating plastic outer shell that can typically be touched during the liquid heating process without injury. Such a device is shown in U.S. Pat. No. 3,931,494 of Fisher. Plastic inner walls are not used in electric liquid containers because these containers are used to boil water, and the container's heating element can become hot enough to melt the plastic inner wall. In addition, a heating element used in association with a plastic inner wall would, compared to metal, take longer to boil water under similar heating conditions.
It is a general object of the present invention to provide an electric drinking cup for vehicles that safely keeps hot beverages, such as coffee, at a safe drinking temperature.
It is a further object of the present invention to use a plastic inner liner and an outer metal shell to form the body of the electric drinking cup of the invention, wherein the plastic inner liner is curved over the upper edge of the outer metal shell to form a safe drinking rim.
It is another object of the present invention to use a heating element, in association with the bottom portion of the plastic inner liner, to slowly heat the beverage therein to a safe drinking temperature.